Minor simplification and cleanup of graph builder.

src/compiler/ast-graph-builder.h

Index: src/compiler/ast-graph-builder.h
diff --git a/src/compiler/ast-graph-builder.h b/src/compiler/ast-graph-builder.h
index ccdb7538a431dea66bf982e7170d0405b3fcb85b..950529a842db2e059e26d11ad0c43ba40aa2f0fc 100644
--- a/src/compiler/ast-graph-builder.h
+++ b/src/compiler/ast-graph-builder.h
@@ -25,8 +25,7 @@ class Graph;
 // of function inlining.
 class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
  public:
-  AstGraphBuilder(CompilationInfo* info, JSGraph* jsgraph,
-                  SourcePositionTable* source_positions_);
+  AstGraphBuilder(CompilationInfo* info, JSGraph* jsgraph);
 
   // Creates a graph by visiting the entire AST.
   bool CreateGraph();
@@ -41,7 +40,8 @@ class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
   class Environment;
 
   Environment* environment() {
-    return reinterpret_cast<Environment*>(environment_internal());
+    return reinterpret_cast<Environment*>(
+        StructuredGraphBuilder::environment());
   }
 
   AstContext* ast_context() const { return ast_context_; }
@@ -57,8 +57,6 @@ class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
   typedef StructuredGraphBuilder::Environment BaseEnvironment;
   virtual BaseEnvironment* CopyEnvironment(BaseEnvironment* env);
 
-  SourcePositionTable* source_positions() { return source_positions_; }
-
   // TODO(mstarzinger): The pipeline only needs to be a friend to access the
   // function context. Remove as soon as the context is a parameter.
   friend class Pipeline;
@@ -114,7 +112,6 @@ class AstGraphBuilder : public StructuredGraphBuilder, public AstVisitor {
   CompilationInfo* info_;
   AstContext* ast_context_;
   JSGraph* jsgraph_;
-  SourcePositionTable* source_positions_;
 
   // List of global declarations for functions and variables.
   ZoneList<Handle<Object> > globals_;